The present invention relates to an apparatus for supporting the material to be treated in continuously operated thermal treatment furnaces, where the supporting of the material is realized by support elements external to the furnace.
From the FI patent 67,726, there is known a material support device to be used in thermal treatment furnaces, wherein on the circumference of a cooled roll, there are placed at least two cooled rolls with essentially smaller diameters. The larger roll, serving as the support device, is installed externally to the thermal treatment furnace, or between two successive thermal treatment furnaces, so that the supporting proper of the material is carried out by means of one circumferentially placed roll at a time. The roll located on the circumference of the larger roll rotates at the rotational velocity of the material to be supported, whereas the mutual position of the circumferentially installed rolls can be adjusted by means of an actuator arrangement connected to the larger roll.
From FIGS. 3 and 4 appended to the FI patent 67,726 it can be seen that the shape of the larger roll, which is formed to conform to the shape of the circumference of the smaller roll and arranged around it, prevents the flowing of gas essentially completely underneath the material to be supported. Thus the temperature of the supported material is at the bottom surface different than at the top surface. On the other hand, the purpose of the design of the larger roll specified in the FI patent 67,726 and illustrated in the drawing is to keep the smaller roll longer in operation by preventing the hot gases from proceeding to the surface of the smaller roll.
The object of the present invention is to eliminate some of the drawbacks of the prior art and to realize an advanced supporting apparatus for material to be treated in thermal treatment furnaces, by means of which apparatus hot gases are made to flow, at the support apparatus, also underneath the material to be supported, without subjecting the smaller roll used for the support proper to an excessive thermal load. The essential novel features of the invention are apparent from the appended claims.
The support apparatus according to the invention for material to be treated in continuously operated thermal treatment furnaces can advantageously be installed essentially near to the orifice of a continuously operated thermal treatment furnace, so that the support apparatus enables an unobstructed flowing of the gas employed in the treatment of the material to be supported, both above and underneath said material. Moreover, the support apparatus constitutes at least part of the thermal treatment furnace sealing. The support apparatus can also be advantageously installed for instance between two continuously operated thermal treatment furnaces, in which case the support apparatus forms part of the sealing of two successive thermal treatment furnaces.
According to the invention, the support apparatus of material to be treated in continuously operated thermal treatment furnaces comprises a housing element, against which at least one support element used for supporting the material is arranged to rest. Against the same housing element, there are advantageously supported two support elements which are installed symmetriccally with respect to the housing element. Moreover, the housing element is installed tumably with respect to the support elements, so that the mutual positions of the support elements can be exchanged by rotating the housing element around it axis. The housing element as such is installed essentially horizontally in the vicinity of the orifice of the continuously operated thermal treatment furnace, so that the housing element is advantageously supported by means of support members provided on both sides of the thermal treatment furnace orifice.
Advantageously the orifice of the thermal treatment furnace is formed of two essentially vertical walls that are interconnected by two essentially horizontal walls which are positioned on different levels. Around the housing element, at the vertical walls of the orifice, at each wall there is installed at least one sealing element, which in part seals the housing element against the thermal treatment furnace, when the support apparatus is in support position. In between the sealing elements providing for the sealing with the vertical walls of the orifice, in connection with the housing element there is installed, advantageously concentrically, one or several elements constituting the sealing together with the horizontal wall, which elements at the same time serve, underneath the material to be supported, advantageously as the control elements of the thermal treatment furnace gas flowing from one thermal treatment furnace to another. In case the number of thermal treatment furnace gas control elements is at least two, in the interval formed by each control element there is advantageously installed, around the housing element of the support apparatus, concentrically at least one intermediate support element. Advantageously the shape of the intermediate support element essentially conforms to the shape of the control element, but it is smaller than the control element, so that when seen from the end of the housing element of the support apparatus, the transversal area of the intermediate support element constitutes 70-90% of that of the respective control element. The intermediate support element can also be installed in the space left between the sealing element and the control element. Thus the intermediate support element can be used in the support apparatus according to the invention also when only one control element is installed around the housing element.
When the support apparatus according to the invention is in operating position, the support element of said apparatus, which advantageously is roller-shaped, supports the material to be supported that proceeds at an essentially high velocity past the support element, so that the support element rotates at an essentially equal velocity with the material to be supported. The control element, installed in connection with the housing element used for supporting the support element, controls the gas of the thermal treatment furnace, so that the gas can also flow underneath the material to be supported.
In order to prevent additional thermal load caused by gas flows on both sides of the support element, the support element is provided with a cooling agent lead-through, in which case there is obtained an essentially efficient heat transfer away from the support element. In heat transfer, there is advantageously used a flow-through type cooling agent circulation. Here the term flow-through type circulation means that the end where the cooling agent is discharged is different from the end where it is fed in. However, the flowing of the cooling agent in connection with the support element can include partial recirculation, in which case the passage of the cooling agent in some parts of the flow is opposite to the flow-through proper. Moreover, the sealing elements of the support element are provided with a lead-through type circulation of the cooling agent, in which case also the housing element of the support apparatus can be protected against an excessive thermal load.
In the support apparatus according to the invention, the sealing element and the control element installed around the housing element are advantageously made of some ceramic material, whereas the intermediate support element provided in between the two control elements is advantageously made of metal.